Best Professor I have ever had. He's difficult, but what good professor isn't right? I never ever ever missed one of his classes even though they were podcast because I enjoyed him so much. I wish he taught more of my classes. Let me rephrase, I wish he taught all of Professor Cheng's classes.

I am currently enrolled in his class.
His lectures are OK. He is almost clear about what he teaches in the class. but he talks so fast that if English is your second language, you would be in trouble understanding the lecture. so you have to record them. (there is podcast available for the class as well) your English should be really good if you wanna take his class, since he asks you to write long essay questions for the exams. and then even if you have written the right answer, he won't give you a fair point, a clear answer has less answer than a long but unclear answer! so write as much as you can on the exam! another problem with the class is that, there is no curve. so if you messed up in one exam, you better drop the class!
good luck!